RESDNS is a small utility who does the reverse IP lookup for your web server, if you have not configured it.
Due to performance reasons and to avoid access problems on your web server, most systems run with the reverse lookup turned off. The biggest problem is, that in the logfile of the server, you only have the IP numbers of your clienst registered.
Since you normally make some statistics of your clients, it would be fine to have the DNS names of your clients.
RESDNS just does this, it replaces the IP-number in the logfile with it's logical DNS name. (As far as the reverse lookup is configured correctly at the client site.
You must have the web logfile in the common logfile format. In this format, the client ip number is stored at the beginning of the line, and is delimited with a blank character.
The usage of RESDNS is very simple. Just start RESDNS and tell it the name of your logfile, and what the destination filename is.
RESDNS will then try to resolve all those IP numbers to hostnames.
RESDNS has some usefull additional commandline options
RESNDS is currently emailware. So if you use it, you must drop me a email message. I like to know where you are located on this globe (or outside <g>), what's the size of the network you manage, what web server you use and what you think about this utility.
Currently we have only one places to download the RESDNS software. But this will change, as soon as we leave the beta stage.
Get the RESDNS windows NT/95 on the internet at www.neatech.ch (42kB)
Get the RESDNS Netware NLM on the internet at www.neatech.ch (38kB)
All users who like, can download the current version to test it's correct function.
If for any chance this utility should not work on your system then send me a message with as much information as possible.
And if you would like to see a missing feature in the utility, then don't hesitate, and ask me. If I find it a usefull feature too, then you have a big chance to get it implemented in a next release.
When a DNS server is asked to resolve a ip number back into a host name, then the answer is cached in the DNS server for some amount of time. But when the server does not get a valid answer (hostname) then no information is saved in the DNS server. (No negative caching, if you have read the DNS book from O'Reily)
When the DNS server is unable to resolve the ip number, the next time it is asked for the name of this ip adress, it does the whole lookup again and again. Normaly this leads to a timeout in the DNS server, and timeouts are currently between 5-30 seconds. So if a client has loaded two pages from your server, with 5 pictures included each, this gives us 2*6 entries in the logfile. And now you try to resolve this ip number 12 times, and always you get a timeout, so this can block the resolusion process for 12*5 up to 12*30 seconds. (1 - 6 minutes)
And now you had 10 such user in a day, so this would give you 10*6 minutes, so ONE hour just to resolve those nasty ip numbers who can't be resolved. (And you are lucky if those users did not load more objects from your web server)
To avoid this problem, RESDNS remembers all (the last 1024 to be correct) not "resolvable" IP numbers, and does not ask the DNS server again.
The NLM version is just a technical test-version, who is quite capable to crash your server, when you try to unload it via the UNLOAD command.
Copyright 1997, NEATECH Andre Schild ("The author")
THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND, EXPRESSED, IMPLIED OR OTHERWISE, INCLUDING AND WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES WHATSOEVER (INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS OF PROFITS, BUSINESS INTERRUPTION, LOSS OF INFORMATION, OR ANY OTHER LOSS) , WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR INABILITY TO USE THIS SOFTWARE.
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